Les articles de la Tour du Valat liées à des projets de restauration écologique

Le choix des états de référence en écologie de la restauration : enseignements de projets menés dans divers écosystèmes

Wed, 26 Aug 2026 11:40:12

de Benjamin Weigel, Maria Alp, Ivan Bernez, Renaud Jaunatre, Marie-Laure Acolas, Didier Alard, Virginie Archaimbault, Christine Argillier, Marie-Lise Benot, Vincent Bertrin, et al.
In Sciences Eaux & Territoires, 50 (August, 2026), 9651-9651
En ligne : revue-set.fr[...]

Defining reference states plays a key role in ecological restoration, guiding management strategies and serving as a benchmark for evaluating ecosystem recovery. However, the choice of reference states is never entirely objective and depends on the context, value-driven approaches, and other numerous criteria such as site history and geographical setting, ecological integrity, or stakeholder interests. To shed light on how reference states are defined, we analyzed 32 restoration projects covering both terrestrial and aquatic ecosystems, monitored between 1999 and 2023 by researchers from the INRAE Ecological Restoration Network (REI, https://restauration-ecologique.hub.inrae.fr ). Our results highlights shared trends in the criteria used to select reference states, while also revealing variable levels of agreement among projects, with notable differences between aquatic and terrestrial projects in terms of stakeholder involvement, selected metrics, and evaluation measures. This study represents a first step before launching a broader survey within the international community. The objective is to further explore the challenges associated with defining reference states, particularly in the context of accelerating global (notably climate) change, and the new EU Nature Restoration Law being implemented across Member States.

Vegetation trajectories over 150 years of temporary ponds created in the Camargue delta (Southern France)

Wed, 18 Mar 2026 15:40:14

de Hugo Fontes, Patrick Grillas, Thierry Dutoit, Antoine Gazaix, Elie Gaget, François Mesléard
In Restoration Ecology, (en ligne) (March, 2026), e70372
En ligne : onlinelibrary.wiley.com[...]

Temporary ponds in the Mediterranean climate have a high conservation value, but many have been severely destroyed or degraded. Pond restoration and new pond creation have been engaged widely. Evaluations of the success of such operations are generally carried out over 10–15 years and show divergent results over this timeframe. In the Camargue (Rhône delta, South of France), several temporary ponds were created with various objectives since the second half of the 19th century.
Study the long-term trajectory of plant communities in created temporary ponds and compare them with those of reference temporary ponds.
We carried out vegetation surveys and measured environmental parameters in 25 ponds created in the 19th, 20th, and 21st centuries, as well as in 27 natural reference ponds (space-for-time substitution approach).
Submerged macrophyte communities (composition, abundance, and species-richness) converged toward the reference communities after one or several decades. Emergent plant communities (terrestrial plants and helophytes) converged more slowly toward the reference communities (composition and abundance). Even after 150 years, the emergent plant communities with the highest conservation interest (in particular Natura 2000 habitat) were not found in created ponds.
The creation of temporary ponds in the Camargue is of conservation interest but cannot compensate for the loss of natural temporary ponds.

Suivi et gestion du Marais restauré de Petit Badon : bilan de période 2023-2025 (2026)

Wed, 26 Aug 2026 11:40:14

de Pauline Rocarpin, Hugo Fontes, Morgan Garnodon, Emilie Laurent, Philippe Lambret, Marion Lourenço, Anthony Olivier, Loic Willm, Thomas Blanchon, Yves Kayser
Arles : Tour du Valat, 2026, 1 vol. (51 p.)

Le projet de restauration du marais de Petit Badon, situé en Camargue, a été lancé en 2017. L'objectif était de recréer un marais temporaire méditerranéen (14 ha) sur une ancienne friche agricole, afin de :
- Restaurer des habitats favorables à la biodiversité (flore, oiseaux, odonates, amphibiens, etc.)
- Étudier la dynamique écologique du site
- Créer un terrain de démonstration pour la pédagogie et la recherche.

Un suivi de la biodiversité a été réalisé de 2023 à 2025 :
- Paysage : Un protocole de suivi photographique (vues aériennes et au sol) a permis d’observer l’évolution de la végétation, notamment l’expansion d’espèces halophytes et aquatiques.
- Flore : La végétation aquatique est dominée par Chara vulgaris et Riella cossoniana, avec une progression d’espèces typiques des marais temporaires (Ranunculus peltatus, Zannichellia palustris). Cependant, des espèces envahissantes comme les tamaris et les massettes se développent, menaçant les espèces annuelles.
- Odonates : 13 espèces ont été recensées, dont Lestes macrostigma (en danger en France), favorisée par les remises en eau tardives. Le site est devenu un refuge pour cette espèce rare.
- Amphibiens : 4 espèces sont présentes, dont la Rainette méridionale (Hyla meridionalis), dont les effectifs ont explosé en 2025. Cependant, des espèces invasives comme les grenouilles vertes (Pelophylax ridibundus) dominent.
- Chiroptères : 13 espèces de chauves-souris ont été identifiées, dont des espèces rares comme la Noctule commune et la Barbastelle d’Europe, confirmant l’importance du site pour ce taxon.
- Oiseaux : 158 espèces ont été observées, dont des nicheurs comme l’Échasse blanche (Himantopus himantopus) et des migrateurs comme la Glaréole à collier (Glareola pratincola). Les effectifs varient selon les années et les conditions hydrologiques.

Gestion hydrologique et actions complémentaires :
- Gestion de l’eau : un plan de pompage adaptatif a été mis en place pour mimer le cycle méditerranéen (mise en eau tardive en automne, assec estival). Cela a permis de réduire les coûts énergétiques et de limiter les nuisances sonores.
- Lutte contre les espèces invasives :
- Végétales : arrachage manuel de Baccharis halimifolia (Sénéçon en arbre), Paspalum distichum, et surveillance des jussies (Ludwigia sp.).
- Animales : Contrôle des grenouilles vertes envahissantes.
- Pâturage : un troupeau de chevaux sauvages de Camargue en rotation permet de limiter la végétation hélophyte et de maintenir un marais "ouvert", favorable aux macrophytes aquatiques.
[résumé rédigé par une IA]

Plant trait responses to herbivore type managed as domestic or as wild

Wed, 16 Jul 2025 15:33:41

de Clémentine Mutillod, Elise Buisson, Laurent Tatin, Gregory Mahy, Marc Dufrene, Nina Morvan, François Mesléard, Thierry Dutoit
In Journal of Environmental Management, 391 (September, 2025), 126378
En ligne : www.sciencedirect.com[...]

The urgency of restoring ecosystems over vast areas has placed rewilding using wild herbivores at the forefront. However, few scientific studies address its effects on biodiversity and ecosystem functioning compared to more traditional conservation interventions with domestic herbivores. Equus ferus przewalskii horses introduced 30 years ago in the National Park of Cévennes, France - as a step of a conservation program of the species for its reintroduction in Mongolia - now occur as a semi-wild horse population, socially natural (i.e., management is based on natural selection). This introduction allowed us to compare this management system (‘as wild’) with other breeding systems: domestic sheep or domestic horses. Rewilding projects especially focus on the restoration of ecological functions, we therefore sought to find out if there are differences in the functional traits of the vegetation depending on the grazer and its management (domestic vs ‘as wild’) with the aim to generalize our results to other rewilding projects. Two levels of organization were tested (1) plant communities – using the TRY database and botanical surveys and (2) plant populations – by selecting four indicator species with traits measured in situ. Our results show that at equivalent grazing pressure, domestic horses or ‘as wild’ horses preserve the same plant functional types as in the traditional reference ecosystem grazed by sheep. Whatever the grazer and its management, grassland plant communities are characterized and dominated by perennial polycarpic plants, with oligotrophic to mesotrophic nutrient requirement, hemicryptophytes, graminoids, plants with entire leaf blades, not spiny, erect and mainly forming tussock. Nevertheless, some interesting significant differences were measured between the plant communities growing under the three types of grazing (e.g., lower functional richness and more plants with entire leaf blade under sheep grazing). Even between horse sub-species, differences were significant for some traits (e.g., more chamaephyte species growing under ‘as wild’ horses), which could be linked to physiological and morphological differences between the two horses sub-species (e.g., nutritional requirements, herbivore size) and by herd management. However, the intraspecific variability on the four quantitative traits measured on four indicator species do not show a general pattern. Although these results are valid at a given time and in a particular ecosystem, the vegetation functional traits approach can help in decision-making regarding ecosystem management choices and highlight the fact that the ‘as wild’ management adds an interesting alternative to conservation.

Projet : Restauration écologique des zones humides : convention n°22043 (2025)

Wed, 25 Mar 2026 13:21:55

de Florence Daubigney, Hugo Fontes, Philippe Lambret, Delphine Nicolas, Anthony Olivier, Loic Willm, Leïla Debiesse
Arles : Tour du Valat, 2025, 1 vol. (82 p.)

A retenir :
- Restauration des sites du Cassaïre et de la Petite Forêt en Camargue
- Restauration de zones humides dégradées et conservation de Lestes macrostigma et autres libellules menacées
- Evaluation de deux projets de restauration de continuité hydroécologique intra-lagunaire avec l’anguille européenne, espèce emblématique et menacée

Quelle utilisation du concept d’écosystème de référence pour évaluer le succès de création de mares temporaires en Camargue ? (2025)

Fri, 12 Sep 2025 16:13:47

de Hugo Fontes
[S.l.] : Université d'Avignon, 2025, 182
En ligne : theses.hal.science[...]

Face à la dégradation des espaces naturels et la perte de biodiversité, la restauration écologique est considérée comme un des outils majeurs de la conservation biologique. Cette discipline récente, fait encore l’objet de controverses en particulier concernant le concept d’« écosystème de référence » considérée comme trop fixiste. Il est cependant aujourd’hui communément admis que la définition d’un écosystème de référence consiste non pas à figer une représentation d’un écosystème « idéal » passé, mais à explorer ses variations tant historiques qu’actuelles. Malgré ces avancées conceptuelles, des lacunes méthodologiques sont encore à combler afin de mieux prendre en compte la variabilité des écosystèmes de référence dans l’évaluation du succès d’opérations de restauration écologique.Pour répondre à ce besoin, nous avons choisi comme cas d’étude les mares temporaires méditerranéennes de Camargue, un écosystème dont les conditions environnementales et les communautés végétales sont particulièrement variables, notamment en raison de l’intermittence des phases aquatiques et sèches. Malgré leurs enjeux de conservation, les mares temporaires méditerranéennes ont connu et connaissent encore de forts impacts anthropiques. En réponse, des opérations de restauration et de création ont été réalisées et nécessitent maintenant d’être évaluées.Dans un premier temps, nous avons développé un indicateur, le « Distance to References Communities Index » (DRCI) qui permet de comparer un site ou une communauté en cours de restauration avec un panel de sites ou de communautés de référence. Cette méthode considère que chaque situation de référence est un objectif potentiel, contrairement aux méthodes couramment utilisées qui considèrent une situation moyenne de référence comme objectif optimal. Le DRCI est un indicateur intégratif qui, focalisé sur les communautés, utilise un indice de distance ou de similarité. Il est particulièrement adapté aux systèmes écologiques variables comme les mares temporaires.Nous avons ensuite exploré la diversité spatio-temporelle des mares de Camargue, au travers de toutes les données floristiques anciennes disponibles et des relevés réalisés dans le cadre de cette thèse dans 27 mares de références en avril, mai, juin et août 2019 et 2020. Les relevés ont permis de retrouver l’essentiel des espèces connues depuis les années 50, avec des proportions comparables. Les mares contemporaines peuvent donc être considérées comme des écosystèmes de référence pertinents, comparables aux mares inventoriées dans la seconde moitié du 20ème siècle. Néanmoins, certains changements mineurs dans la végétation des mares peuvent être interprétés comme des dégradations, avec notamment l’apparition d’espèces exotiques envahissantes et des phénomènes de salinisation potentiellement liés au changements climatiques.Enfin, nous avons comparé la végétation de 25 mares créées aux 19ème, 20ème et 21ème siècle (inventoriées en avril, mai, juin et juillet 2020) avec celle des 27 mares de références. Les communautés végétales (composition et abondance des espèces) des mares créées au 21ème siècle sont bien distinctes des communautés de références, contrairement aux communautés des mares créées antérieurement. Les communautés en conditions inondées sont plus proches des communautés de références que les communautés de la phase sèche. En particulier, les espèces émergentes protégées et menacées sont généralement absentes des mares créées, contrairement aux macrophytes submergés. L’intérêt de la création de mares temporaires méditerranéennes est donc important pour les communautés aquatiques, mais reste limité pour certaines communautés terrestres et amphibies.Le choix du modèle de référence et des variables mesurées peuvent fortement influencer les résultats et les conclusions de l’évaluation. La définition d’un modèle de référence revient à définir les objectifs de projets de restauration et rend donc plus ou moins flexible leur évaluation.

The Distance to Reference Communities Index (DRCI): a new tool to assess communities' restoration success

Mon, 27 May 2024 15:18:01

de Hugo Fontes, Christian Marquis, Franck Torre, Patrick Grillas, Thierry Dutoit, François Mesléard
In Restoration Ecology, (Online version) (May, 2024), e14194
En ligne : onlinelibrary.wiley.com[...]

The concept of a reference ecosystem is fundamental in restoration ecology, especially in assessing the success of ecological restoration projects. In response to criticism, it has undergone conceptual evolutions in its definition and use in the last decades. Even though there is still a need to develop statistical methods and analyses to account for reference variability. Here, we focus on two original and one literature-based calculation methods for designed indexes, which all aim to compare a community to be assessed (undergoing restoration) with a variable set of reference communities. These methods either use the average reference situation (species composition and abundance) as the restoration target or on the contrary, allow any reference site to be considered a relevant target. We compare the results of these methods by analyzing a simulated dataset. We then illustrate the application of the most relevant index by a real case study that compared a created Mediterranean temporary pond to a panel of 27 reference ponds located in the south of France. The results show that the Distance to Reference Communities Index (DRCI) correctly measures differences in species composition and abundance between an assessed and a reference panel of communities. It takes into account the variability of the reference communities, while the use of other indexes focuses on unrealistic average and fixed reference values. DRCI is complementary to a detailed ecological interpretation and to the use of other commonly used indexes, by giving a synthetic metric.

Projet : Restauration écologique des zones humides : convention n°22043 (2024)

Wed, 25 Mar 2026 13:21:58

de Florence Daubigney, Hugo Fontes, Philippe Lambret, Delphine Nicolas, Anthony Olivier, Olivier, Loic Willm
Arles : Tour du Valat, 2024, 115

A retenir :
- Restauration des sites du Cassaïre et de la Petite Forêt en Camargue
- Restauration de zones humides dégradées et conservation de Lestes macrostigma et autres libellules menacées
- Evaluation de deux projets de restauration de continuité hydroécologique intra-lagunaire avec l’anguille européenne, espèce emblématique et menacée

Utiliser des fourmis pour restaurer la nature ? (2024)

Tue, 24 Sep 2024 09:46:17

de Thierry Dutoit, Adeline Bulot, Tania De Almeida, François Mesléard, Olivier Blight, Eric Fouilland, Françoise Gourmelon
[S.l.] : CNRS éditions, 2024, 180-184
En ligne : hal.science[...]

La majorité des méta-analyses réalisées à travers le monde sur la mesure du succès des opérations de restauration écologique d’écosystèmes dégradés a montré qu’il semblait impossible de restaurer l’intégralité des écosystèmes préexistants même avec la mobilisation de moyens techniques (génie civil) et financiers considérables. C’est pourquoi, de nouvelles interventions basées sur de l’ingénierie écologique encore appelée solutions fondées sur la nature, sont préconisées actuellement pour accroître le succès de la restauration des écosystèmes mais aussi, pour limiter leurs coût économiques et environnementaux dans un contexte de changements globaux. Le 7 août 2009, plusieurs millions de litres d’hydrocarbures se sont déversés en plein centre de la plaine de Crau dans les Bouches-du-Rhône suite à la rupture accidentelle d’un oléoduc. Cinq hectares d’un écosystème steppique unique au monde fut totalement détruit. Après les phases de réparation de l’oléoduc et de dépollution du site par évacuation des terres polluées en décharge (72 000 tonnes), un transfert de sol prélevé dans une carrière proche a été réalisé. Pour compléter cette opération de génie civil, des reines fondatrices d’une fourmi moissonneuse du genre Messor, ont été réimplantées. Cette première mondiale allait-elle permettre alors d’accélérer la restauration de l’écosystème steppique qui préexistait avant l’accident ?

Ants in restoration ecology: Why, what's and the way forward

Wed, 20 Dec 2023 15:41:18

de Tania De Almeida, Xavier Arnan, Yvan Capowiez, Mickaël Hedde, François Mesléard, Thierry Dutoit, Olivier Blight
In Land Degradation and Development, December (December, 2023)
En ligne : cnrs.hal.science[...]

Global changes call for more nature‐based solutions, especially in nature conservation involving ecological restoration. Current methods essentially based on civil engineering are both expensive and costly in non‐renewable energy consumption and pollution terms. The non‐sustainability of these techniques is leading to the direct use of certain species to restore degraded ecosystems. Ants, because of their central role in ecosystem functioning and their occurrence on almost all terrestrial ecosystems, are promising candidates for environmental monitoring and such ecological restoration projects. We provide here a narrative review of the ecological functions performed by ants, and we take stock of how ants are currently considered in passive and active restoration. We then propose a trait‐based approach to facilitate their use by practitioners in future restoration projects. We list and discuss both life‐history traits relevant for environmental monitoring and functional traits known to affect abiotic (physical and chemical soil properties) and biotic (plant and fauna communities) components.

Eco-grazing and vegetation restoration in Mediterranean wetlands (2023)

Wed, 21 Feb 2024 15:53:46

de François Mesléard
Le Sambuc, Arles : Tour du Valat, 2023, 166
En ligne : s.42l.fr[...]

How can extensive grazing be used to restore Mediterranean wetlands according to the specific features and constraints of a site and the objectives being pursued? What approach should be adopted before implementing pastoral management? What choices should be made considering medium- and long-term possibilities? How can we ensure that current restoration work is running smoothly, so that we can change the methods being used as needed? How can we measure success? This document was written to help those facing these questions. It does not, however, offer a universal recipe or one that can be applied as is. Every site is unique and is characterised by numerous specificities, which means that grazing-based management that is appropriate for one site is unlikely to be so for another if it is reproduced identically.

Éco-pâturage et restauration de la végétation dans les zones humides méditerranéennes (2023)

Fri, 16 Feb 2024 11:22:38

de François Mesléard
Le Sambuc, Arles : Tour du Valat, 2023, 168
En ligne : tourduvalat.org[...]

Comment, sous différentes modalités, le pâturage extensif peut-il être utilisé pour la restauration de zones humides méditerranéennes en fonction du site, de ses spécificités et contraintes, des objectifs visés ? Quelle approche adopter avant de mettre en place une gestion pastorale ? Quels choix effectuer en fonction des possibilités à moyen et long terme ? Comment s’assurer du bon déroulé de la restauration en cours afin d’opérer, si nécessaire, d’éventuelles modifications dans les modalités choisies ? Comment en mesurer le succès ? Le document se propose d’accompagner la réflexion des personnes confrontées à ces questions. Il n’offre cependant pas de recette universelle ou applicable telle quelle. Chaque site est singulier, défini par de nombreuses particularités en raison desquelles une gestion par le pâturage adéquate pour un site a peu de chance de l’être pour un autre si elle est reproduite à l’identique.

La restauration des écosystèmes : de l'amélioration des services écosystémiques à la restauration écologique (2023)

Mon, 11 Dec 2023 14:18:13

de Léo Rocher, Léa Saby, Romane Blaya, Sarah Kubien, Emile Melloul, Clémentine Mutillod, Aure Durbecq, Armin Bischoff, Olivier Blight, Thierry Dutoit, et al.
Saint Pierre (La Réunion), Réunion : IUT de Saint Pierre, 2023
En ligne : hal.science[...]

La restauration des écosystèmes : de l'amélioration des services écosystémiques à la restauration écologique

Evaluation du succès de création de mares temporaires en Camargue Ce qui est restauré et ce qui ne l’est pas (2023)

Fri, 22 Sep 2023 15:37:26

de Hugo Fontes, Patrick Grillas, Thierry Dutoit, Antoine Gazaix, François Mesléard
Arles (FRA) : Tour du Valat, 2023, 131

L’objectif de la présente étude est de réaliser une évaluation du succès de la création de 25 mares temporaires en Camargue, en comparant ces écosystèmes à un ensemble varié de mares de références et en intégrant leur variabilité temporelle. Cette évaluation analysera notamment ce qui a été restauré et ce qui ne l’a pas été.

Restauration du Marais de Petit Badon. Initiation du projet, travaux et résultats des deux premières années de suivi (2023)

Fri, 22 Sep 2023 15:36:36

de Hugo Fontes, Anthony Olivier, Yves Kayser, Emilie Laurent, Marion Lourenço, Olivier Pineau, Pauline Rocarpin, Loic Willm, Patrick Grillas
Arles : Tour du Valat, 2023, 71

Le site du Petit Badon se situe au sud-est de l’ile de Camargue, sur le cours d’un ancien bras du Rhône, celui du Bras de Fer. Le site prend place dans un contexte paysager agricole et de marais, à environ 11km de la mer au sud et à 3,5km à l’est du Rhône actuel. Le terrain est la propriété de la SCA du Domaine du Petit Badon dont les propriétaires sont à l’origine du projet de création de ce marais. Le site, avait été aménagé en exploitation agricole avec une production céréalière (riz notamment) depuis le XIXème siècle jusque dans les années 2000 et a ensuite été pâturé par des chevaux. L'activité agricole avait été certifiée Agriculture Biologique depuis le début des années « 90 » (entre 1990 et 1993). A la demande de la SCA du Domaine du Petit Badon, un projet de création de marais a été initié en 2017 et confié à la Fondation Tour du Valat.
Les objectifs de ce projet sont les suivants :  Recréer un marais temporaire (14 ha) sur une friche agricole avec un fonctionnement proche du cycle hydrologique méditerranéen ;  Reconstituer des habitats favorables pour la biodiversité, notamment méditerranéenne (flore, oiseaux d’eau, odonates, amphibiens, reptiles aquatiques, ...) ;  Etudier la dynamique de reconstitution de l’écosystème ;  Disposer d’un terrain de démonstration pour la restauration des zones humides à des fins pédagogiques et scientifiques. Les opérations de création rentrent dans le cadre conceptuel de l’écologie de la restauration au sens large. Ici, le modèle de référence est un marais temporaire, écosystème bien connu en Camargue, largement détruit par le développement de l’agriculture au cours du siècle dernier et à forte valeur patrimoniale. Le présent projet ne peut cependant pas être qualifié de restauration stricto sensu car il ne vise pas à retrouver la ou les écosystèmes présents tel qu’ils étaient avant leur destruction par l’agriculture, mais s’en inspirent pour concevoir le projet de création.

Restaurer les zones humides méditerranéennes : Le nouveau guide du décideur politique pour une gestion durable et une restauration des écosystèmes d'ici 2030 (2023)

Mon, 18 Sep 2023 17:57:05

de Wetland-Based Solutions initiative, Bruno Boz, Giuseppe Dodaro, Lisa Ernoul, Francesca Etzi, Javier J. Forray, Teresa Gil, François Mesléard, Alessio Satta, Vania Statzu, et al.
[S.l.] : The Mava Foundation, 2023, 62
En ligne : www.wetlandbasedsolutions.org[...]

La restauration des zones humides méditerranéennes est un nouveau manuel à l'usage des décideurs politiques pour la gestion durable et la conservation de l'eau d'ici à 2030. Il s'agit d'un résultat des partenariats intersectoriels partageant le savoir-faire dans le cadre de la Décennie des Nations Unies pour la restauration des écosystèmes 2021-2030. Coordonné par le WWF Espagne, MedWet et la Tour du Valat en partenariat avec l'initiative PIM et MEDSEA, le manuel fait partie de l'initiative Wetlands-Based Solutions et est financé par la Fondation MAVA. Les lecteurs y trouveront des conseils sur l'élaboration et la mise en œuvre d'initiatives de restauration des zones humides ainsi que des critères de sélection des sites. Des experts dans le domaine partagent leurs expériences et études de cas de restauration intégrée utilisant des solutions.

The Cassaïre wetland restoration project: defining the reference ecosystem

Tue, 20 Sep 2022 11:33:53

de Isabelle Muller, Johan Friry, Elise Buisson, François Mesléard
In Ecologia Mediterranea, 48(1) (June, 2022), 10

Defining a reference ecosystem for ecological restoration project is an essential step. The reference can correspond to the historical ecosystem, can be defined to solve environmental issues or can correspond to a socioecosystem. For the restoration of the Cassaïre site in the Camargue delta in southern France, the reference ecosystems chosen are: Mediterranean temporary wetlands and Mediterranean meso-xeric grasslands. The choice of these two reference ecosystems appears logical considering their contribution to regional biodiversity. Temporary wetlands and meso-xeric grasslands are rare, adapted to the Mediterranean climate, seriously endangered and host a high species richness. They are potentially achievable restoration targets because patches of these ecosystems remain in the Camargue area and close to the Cassaïre site. Moreover, an ecological history approach reveals deep human imprints on ecosystems and ensures that historical restoration targets (the state prior to human impacts) cannot be reached, because they are associated with hydraulic functioning (flooding of the Rhône and Durance) that no longer exists. The restored site is planned to be suitable for livestock grazing, thus presenting a new agricultural opportunity, while simultaneously offering new services, such as hunting.

Altering native community assembly history influences the performance of an annual invader

Wed, 26 Jan 2022 14:48:03

de Manon C.M. Hess, François Mesléard, Truman P. Young, Benoit de Freitas, Nathan Haveneers, Elise Buisson
In Basic and Applied Ecology, 59 (March, 2022), 70-81
En ligne : linkinghub.elsevier.com[...]

Understanding the determinants of early invasion resistance is a major challenge for designing plant communities that efﬁciently repel invaders. Recent evidence highlighted the signiﬁcant role of priority effects in early community assembly as they affect species composition, structure and functional properties, but the consequences of native community assembly history on the success of subsequent invasions has not been elucidated yet. In a greenhouse experiment, we investigated how (1) the identity of the ﬁrst native colonizing species (one of two grasses: Dactylis glomerata and Lolium perenne, or two legumes: Onobrychis viciifolia and Trifolium repens), each introduced four weeks before the rest of the native community, and (2) timing of species establishment (synchronous vs. sequential sowing), inﬂuenced early establishment success of Ambrosia artemisiifolia, an annual noxious weed in Europe. First colonizer identity and establishment timing both affected early biomass production and composition of the community, and had implications for A. artemisiifolia early invasion success. Invasion success decreased when all native individuals were sown simultaneously, quickly generating a high biomass production, while it increased when the productive N-ﬁxing legume T. repens was sown ﬁrst. These ﬁndings support that native species assembly history matters to invasion resistance in the early growth stages, thus opening the way to more effective invasive species management strategies in restoration.

Restoring Mediterranean Wetlands: The new policymaker’s playbook for sustainable management and ecosystem restoration by 2030 (2022)

Wed, 1 Feb 2023 11:05:23

de Wetland-Based Solutions initiative, Bruno Boz, Giuseppe Dodaro, Lisa Ernoul, Francesca Etzi, Javier J. Forray, Teresa Gil, François Mesléard, Alessio Satta, Vania Statzu, et al.
[S.l.] : The Mava Foundation, 2022, 60
En ligne : www.wetlandbasedsolutions.org[...]

Restoring Mediterranean Wetlands is a new policymaker’s playbook for sustainable management and conservation of water by 2030. It is an output of the intersectoral partnerships sharing know-how as part of the United Nations Decade on Ecosystem Restoration 2021-2030. Coordinated by WWF Spain, MedWet and Tour du Valat in partnership with PIM Initiative and MEDSEA, the playbook is part of the Wetlands-Based Solutions initiative and funded by the MAVA Foundation. Readers can expect guidance on developing and implementing wetlands restoration initiatives and criteria on selecting sites. Experts in the field share experiences and case studies of integrated restoration using nature-based solutions and how to set clear objectives, identify priorities and undertake continuous evaluation.

Projet MediCyn - Rapport d’activités 2021 (2022)

Tue, 13 Sep 2022 14:23:43

de Philippe Lambret, Hugo Fontes, L. Quoniam, C. Reljic
Arles : Tour du Valat, 2022, 25 + annexes

Le projet MediCyn, porté par le Grand port maritime de Marseille (GPMM) et monté en partenariat avec la Tour du Valat (TdV), vise à améliorer l’état de conservation et la valeur écologique de deux sites d’un des secteurs « à enjeux » du Plan Rhône- Saône 2015-2020 : Le Grand clos et le Relai, tous deux en zone Natura 2000 et au sein de la couronne agri-environnementale du GPMM.
Trois modes de gestion hydraulique seront testés, avec les modes 1 et 2 visant à contrôler si les effets du mode 3 sont ceux attendus :
▪ mode 1 – gestion actuelle « type marais de chasse traditionnel » avec une mise en eau en juillet et un maintien du niveau d'eau jusque novembre par pompage, puis assèchement naturel dont la période dépend des précipitations ;
▪ mode 2 – gestion type « marais temporaire méditerranéen », avec une mise en eau naturelle (les précipitations ont lieu essentiellement à l’automne) et éventuellement par pompage en décembre afin d’éviter les conditions d'une année particulièrement défavorable (faible probabilité), et veille au maintien du niveau d'eau jusque début mai (éventuellement par pompage), puis assèchement naturel ;
▪ mode 3 – gestion intermédiaire : mise en eau début octobre et maintien du niveau d'eau par pompage jusque fin avril, puis assèchement naturel. L'hypothèse générale est que cette gestion innovante (mode 3) favorise la conservation de la nature et la valeur pastorale des milieux sans modifier de façon significative leur intérêt cynégétique. Pour ce faire, la réalisation de travaux de réfection du réseau hydraulique et des aménagements a été programmée sur le Grand clos et le Relai. Ceux-ci permettront la mise en place de l’expérimentation décrite ci-dessus dont les effets seront mesurés à travers différents suivis. Ces suivis concerneront des paramètres de milieux (niveaux d’eau, conductivités, gestion hydraulique, niveaux trophiques abiotiques), les activités cynégétique et pastorale (tableaux de chasse, calendrier et pression de pâturage, végétation fourragère, satisfaction des usagers des sites i.e. chasseurs et manadiers), des compartiments de la biodiversité (plantes émergées et immergées, macro-arthropodes dont les libellules, oiseaux d’eau chassables

Grazing in temporary paddocks with hardy breed horses (Konik polski) improved species-rich grasslands restoration in artificial embankments of the Rhône river (Southern France)

Fri, 15 Oct 2021 08:27:18

de Cannelle Moinardeau, François Mesléard, Hervé Ramone, Thierry Dutoit
In Global Ecology and Conservation, Online (October, 2021), 16
En ligne : www.sciencedirect.com[...]

Extensive horse grazing with hardy breeds is largely used in conservation management for restoring species-rich semi-natural grasslands in Europe. As an example, the Donzère-Mondragon Rhône river embankments (south-eastern France) where horse grazing with Konik polski succeeded to maintain high species richness in patches of open and short grassland, but failed for patches of tall grassland dominated by the grass tussock species Brachypodium phoenicoides. In response, an increase of herd density by the creation of temporary paddocks was applied in tall grassland patches. Grazing pressure over time between patches was estimated via GPS fixed to mares, biomass, plant species richness measurements and from multispectral photographs, the normalized Difference Vegetation Index (NDVI) was calculated. Finally, telemetric data were collected. We wondered if the use of extensive horse grazing with temporary paddocks occupation, increase plant species richness. After three years, our results show that the increase in stocking rate enabled a significant increase of plant species richness in the tall grassland patches, with a significant decline of B. phoenicoides in all paddocks. The NDVI was strongly correlated with herbaceous biomass and plant species richness, while the number of GPS points indicating the position of the mares was higher in areas where the NDVI was high. These results are discussed for improving horse grazing conservation systems efficiency on grasslands established in anthropized sites such as embankments and the use of the NDVI as an appropriate tool to help decision-making for large-scale applications.

Key issues in Northwestern Mediterranean dry grassland restoration

Wed, 19 May 2021 12:24:02

de Elise Buisson, Tania De Almeida, Aure Durbecq, André J. Arruda, Christel Vidaller, Jean‐François Alignan, Tiago S. P. Toma, Manon C.M. Hess, Daniel Pavon, Francis Isselin‐Nondedeu, et al.
In Restoration Ecology, 29(S1) (April, 2021), 10
En ligne : onlinelibrary.wiley.com[...]

Dry grasslands of the Northwestern Mediterranean Basin are seminatural species-rich ecosystems, composed of many annual species and some structuring perennial species. As these grasslands have been used as rangelands for centuries, human management (grazing; ﬁre regimes) is one of their main ecological and evolutionary drivers, along with the Mediterranean climate. Despite EU conservation policy, damage to such grasslands still occurs and efﬁcient ecological restoration is needed. This article reviews restoration constraints, effective techniques, and research perspectives for restoring them in the light of their ecological characteristics. Major restoration constraints speciﬁcally include (1) a poor contribution of the internal (seed bank) and external (seed rain) species pools, and (2) low establishment of some perennial species. The latter may be the result of the low seed quantity or quality of perennial species, stochastic or extended droughts, high soil nutrient content that may lead to competition (e.g. between weed and target species), inappropriate grazing management or ﬁre regimes leading to shrub encroachment, or the death of target species seedlings in early stages of restoration. Successful restoration techniques include seeding, transplanting, hay transfer, and timely soil transfer, all of which have to be adapted to regional plant phenology and to local Mediterranean climate. They must be combined with appropriate grazing or ﬁre management. Their success may depend on years with particular rainfall amounts or patterns or on particular target plant species. We discuss research perspectives contributing to a better understanding of seed dispersal, seedling recruitment, and soil processes and suggest the beneﬁts of using ecosystem engineer species.

Dynamics of reedbed vegetation and impacts of management in Lesser Prespa Lake wetlands. Final report and synthesis 2017 - 2021. Report within the LIFE15 NAT/GR/000936 Bird conservation in Lesser Prespa: benefiting local communities and building a climate change resilient ecosystem (2021)

Mon, 4 Oct 2021 17:56:18

de Patrick Grillas, Fane Sakellarakis, Gaëtan Lefebvre, Loic Willm, Hugo Fontes, Clémence Pechinot
Arles (FRA) : Tour du Valat, 2021, 105

During the course of the LIFE Prespa Waterbirds project (2017-2021), and regarding the actions regarding the vegetation management and ecology, the main objectives were:
I. The identification of the spatial occupancy and dynamics of T. angustifolia and P. australis with emphasis given on the understanding of their ecological niches as well as detecting the main driving factor(s) for vegetation change, and II. Monitoring the effects of the management actions (cutting and/or grazing) applied towards the restoration of wet meadow communities along the shoreline of Lesser Prespa.
In this framework the detailed objectives set for our study were further divided in:
Assessing the current dynamics in the reedbeds (Phragmites australis / Typha angustifolia) of Lesser Prespa through drone derived orthophotomosaics.
Synthesis of annual mapping of areas burnt by wildfires during the LIFE Prespa Waterbirds using remote sensing techniques on Sentinel-2 and UAV derived orthophotomosaics.
Identification of the ecological niches of T. angustifolia and P. australis.
Effects of submergence after winter cutting on Phragmites australis.
Spatial and structure dynamics of P. australis and T. angustifolia at their patches interface.
Effects of management (mowing + cutting) on the restoration of wet meadows communities.

Key issues in North-western Mediterranean dry grassland restoration

Wed, 30 Sep 2020 16:41:18

de Elise Buisson, Tania De Almeida, Aure Durbecq, André J. Arruda, Christel Vidaller, Jean-François Alignan, Tiago Shizen P. Toma, Manon C.M. Hess, Daniel Pavon, Francis Isselin‐Nondedeu, et al.
In Restoration Ecology, Online (October, 2020), rec.13258
En ligne : onlinelibrary.wiley.com[...]

Dry grasslands of the North-western Mediterranean Basin are semi-natural species-rich ecosystems, composed of many annual species and some structuring perennial species. As these grasslands have been used as rangelands for centuries, human management (grazing; fire regimes) is one of their main ecological and evolutionary drivers, along with the Mediterranean climate. Despite EU conservation policy, damage to such grasslands still occurs and efficient ecological restoration is needed. This paper reviews restoration constraints, effective techniques, and research perspectives for restoring them in the light of their ecological characteristics. Major restoration constraints specifically include i) a poor contribution of the internal (seed bank) and external (seed rain) species pools, and ii) low establishment. The latter may be the result of the low seed quantity or quality of perennial species, stochastic or extended droughts, high soil nutrient content that may lead to competition (e.g. between weed and target species), inappropriate grazing management or fire regimes leading to shrub encroachment, or the death of target species seedlings in early stages of restoration. Successful restoration techniques include seeding, transplanting, hay transfer and timely soil transfer, all of which have to be adapted to regional plant phenology and to local Mediterranean climate. They must be combined with appropriate grazing or fire management. Their success may depend on years with particular rainfall amounts or patterns or on particular target plant species. We discuss research perspectives contributing to a better understanding of seed dispersal, seedling recruitment and soil processes and suggesting the benefits of using ecosystem engineer species. This article is protected by copyright. All rights reserved.

Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands

Wed, 23 Sep 2020 14:13:49

de Tania De Almeida, François Mesléard, M. Santonja, Raphael Gros, Thierry Dutoit, O. Blight
In Proceedings of the Royal Society B: Biological Sciences, 287(1935) (September, 2020), 10
En ligne : royalsocietypublishing.org[...]

Within a local assemblage, ecosystem engineers can have major impacts on population dynamics, community composition and ecosystem functions by transforming or creating new habitats. They act as an ecological filter altering community composition through a set of environmental variables. The impact of ants on their environment has been widely studied, but their multi-component effects (both trophic and non-trophic) have been rarely addressed. We investigated the roles of Messor barbarus, one of the commonest harvester ant species in south-western European Mediterranean grasslands. We analysed soil physico-chemical parameters, above-ground vegetation (e.g. species richness, plant community, micro-local heterogeneity, plant biomass) and above- and below-ground fauna (macrofauna, Collembola, Acari and nematodes). A clear and strong local impact of M. barbarus on soil, vegetation and fauna compartments emerges. The environmental filter is altered by modifications to soil physico-chemical properties, and the biotic filter by changes to plant communities and altered above- and below-ground fauna abundance, occurrence and community structure. The engineering activity of M. barbarus affects not only these separate ecosystem components but also the trophic and non-trophic relationships between them. By altering ecological filters at a local scale, M. barbarus creates habitat heterogeneity that may in turn increase ecological niches in these highly diverse ecosystems.
Keywords :

Giving recipient communities a greater head start and including productive species boosts early resistance to invasion

Tue, 16 Jun 2020 16:58:31

de Manon C.M. Hess, Elise Buisson, Hugo Fontes, Léo Bacon, Florent Sabatier, François Mesléard
In Applied Vegetation Science, 23(3) (July, 2020), avsc.12502
En ligne : onlinelibrary.wiley.com[...]

Methods: In a pot experiment, we simulated invasion by three major invasive species (Ambrosia artemisiifolia, Bothriochloa barbinodis, and Cortaderia selloana) in soil covered with recipient communities differing in species composition (one, three or nine species), density (700 or 2,778 seeds/m2), and time advance (established one or five months previously). We assessed early invasion success by measuring seedling emergence and survival over six months.
Results: Early invasion success was mainly explained by recipient community's time advance and composition (or their interaction), while density had limited influence. Polycultures (three or nine species) showed generally greater invasion resistance, most likely due to high above-ground biomass essentially produced by two species. Species composition interacted with time advance in two ways: (a) Bothriochloa barbinodis seedling emergence was impacted by composition only in communities having five months of advance, suggesting that the contribution of species composition to invasion resistance varies according to the age of the community, and (b) Ambrosia artemisiifolia and Cortaderia selloana survival was affected by time advance in polycultures only, which produced much more biomass than monocultures, implying that a greater head start provides a competitive advantage only if it allows a sufficient increase in biomass production.
Conclusions: Implementing revegetation as soon as site clearance work is over, as well as establishing productive native species may help reduce invasion success. How much of an advantage recipient community time advance represents depends on biomass production.

Harvester ants as ecological engineers for Mediterranean grassland restoration: Impacts on soil and vegetation

Tue, 21 Apr 2020 15:24:18

de Tania De Almeida, Olivier Blight, François Mesléard, Adeline Bulot, Erick Provost, Thierry Dutoit
In Biological Conservation, 245 (May, 2020), 8
En ligne : linkinghub.elsevier.com[...]

Although not widely used, ecosystem engineers represent a promising and sustainable tool in nature-based ecosystem management and restoration. In grassland ecosystems, a few invertebrates that engineer soils have been identified as key species regulating soil nutrients and plant communities' diversity and dynamics. Here, we assessed the role of the harvester ant Messor barbarus, an ecological engineer, in a Mediterranean dry grassland under restoration by characterising its nest environment, particularly the soil and vegetation. We found profound differences in soil physical and chemical variables and plant community structure between nests and antfree patches in the restored grassland. Messor barbarus has improved soil fertility, driven the seed bank towards the reference grassland and significantly increased plant biomass, species richness and micro-local-heterogeneity. As biological filters, M. barbarus has driven plant communities towards a new trajectory in the restored site. Ant patches are characterised by mesotrophic species, whereas ant-free patches are dominated by species characteristic of compacted soils. They have accelerated the ecological recovery of Mediterranean dry grassland plants by directly and indirectly facilitating their re-establishment. These results illustrate the potential key role of ants as ecological engineers for the conservation and restoration of Mediterranean grasslands.

Using limiting similarity to enhance invasion resistance: Theoretical and practical concerns

Mon, 6 Jan 2020 16:06:35

de Manon C.M. Hess, Elise Buisson, Renaud Jaunatre, François Mesléard
In Journal of Applied Ecology, 57(3) (March, 2020), 7
En ligne : onlinelibrary.wiley.com[...]

The control of invasive species is a central topic of both applied and theoretical research. Understanding how and which ecological theories can be used to improve invasion resistance of plant communities is essential, to design effective control strategies.
The theory of limiting similarity, stating that coexistence between species is more limited by competitive exclusion when species share niche properties, is often considered by applied ecologists as a possible approach to limiting plant invasions at the local scale.
The complexity of measuring ecological niche overlap between species as well as the difficulty of disentangling niche from fitness processes currently limit the demonstration and application of this theory. Limiting similarity appears to operate at a time-scale that is too long for efficient impact on invasive species' early establishment. It may also be ineffective against invasions in the long term, due to environmental changes and community instability. Finally, limiting similarity is not applicable to the most common situations, where there are multiple co-occurring invasive species or no prior identification of potential invasives.
Whether the theory of limiting similarity, predicting competitive exclusion when species display niche similarities, can be successfully applied to limit plant invasions—or not—is an important issue for practitioners facing invasive species. In practice, using limiting similarity to design invasion-resistant plant communities appears to be complex, ineffective and unsuitable for most common situations.

Using mechanical clearing and goat grazing for restoring understorey plant diversity of embankments in the Rhône valley (Southern France)

Mon, 9 Dec 2019 10:31:08

de Cannelle Moinardeau, François Mesléard, Hervé Ramone, Thierry Dutoit
In Plant Biosystems, Online (October, 2019), 1-11
En ligne : doi.org[...]

Consumption by animals remains one of the key points to assess the effectiveness of grazing impacts in woodland for increasing understorey plant diversity. To limit the spread of the brambles and restore understorey plant diversity on an artificial embankment an original system of clearings connected by paths was created by mechanically crushing brambles and allowing them to be grazed by rustic goats. The analysis of the indices of consumption of bramble under GIS has been used to provide an estimation of the volume ingested and an estimation of the effectiveness of the goats. The impacts of three different managements (goat grazing, brush clearing and grazing, clearing and exclusion of grazing) and control without management were then tested during a three-year period. The monitoring of the vegetation on permanent plots provided evidence that goat grazing significantly increased in the short term the species-richness and heterogeneity of herbaceous plants communities, in complement with prior clearing. Thus, the objectives of the managers to open up the area and reduce the bramble cover were achieved, but the prior introduction of goats and the installation of mobile enclosures would be advisable in order to ensure the sustainability of these measures on plant diversity in the long term.

Soil compaction enhances the impact of microwave heating on seedling emergence

Tue, 1 Oct 2019 00:00:00

de Elise Buisson, François Mesléard
In Flora, 259 (October, 2019), 151457
En ligne : linkinghub.elsevier.com[...]

An innovative microwave-based process to control invasive species in the ﬁeld is currently under development. We investigated the eﬀect of soil compaction levels under three microwave treatment pairings of power and duration (2kW4 min, 2kW8min and 4kW4 min), on seedling emergence of a diverse seed bank and three major invasive species in Europe (bohemian knotweed, giant goldenrod and jimsonweed). When soil was compacted, the number of seedling emergences of dicotyledons was signiﬁcantly reduced by the 2kW4 min treatment. Furthermore, while some dicotyledon and giant goldenrod’s seedling emergences were observed respectively in plain soil in the 4kW4 min and 2kW4 min treatments, no seedling was recorded in compacted soil for the same treatments. Our results suggest that compacting soil increases the efficiency of microwave heating on seeds. Soil compaction level should therefore be considered in the design of the ﬁnal microwave-based process.

Priority effects: Emerging principles for invasive plant species management

Tue, 1 Jan 2019 00:00:00

de Manon C.M. Hess, François Mesléard, Elise Buisson
In Ecological Engineering, 127 (2019), 48-57
En ligne : linkinghub.elsevier.com[...]

Many anthropic activities generate soil disturbances, favoring competitive, fast growing invasive plant species at the expense of natives. Active restoration of invasion-resistant plant communities is increasingly recognized as a relevant strategy to combat invasive plant colonization in disturbed areas, but results are often unsatisfying. Historical eﬀects, referred as “priority eﬀects” (i.e. the eﬀects generated by the order in which species arrive at a local site), can have a major role in community assembly and invasion success because they involve early colonists altering the performance of later colonists. Taking these priority eﬀects into account in restoration projects is emerging as a relevant way to improve native species restoration success and prevent invasion. The present review discusses two strategies considering priority eﬀects that would help to achieve the classic restoration goal of “more natives, less invasives”. The ﬁrst strategy relies on tackling priority eﬀects of invasive plants using diﬀerent management options adapted to local environmental conditions, including removal, reduction of propagule sources, or mitigation of soil legacies. Indeed, invasive plants often generate strong priority eﬀects providing themselves a substantial competitive advantage through early emergence and quick growth, but also self-induced soil modiﬁcations that can persist after their removal or death, commonly termed “soil legacies”. In fertile and stable conditions, the reduction of invasive species priority eﬀects must be coupled with the restoration of an invasion-resistant native plant cover to avoid reinvasion and secondary invasions. The second strategy is to bring about situations in which the restored native species are more likely to exert strong priority eﬀects, decreasing invasion success. For this purpose, we sketch possible options open to restorationists based on resource or non-resource mechanisms. First, we discuss ways to maximize resource preemption by extending the time advance given to restored native species and manipulating restored species characteristics. Second, we consider the potential eﬀect of increasing niche overlap between native and invasive species. Third, we introduce the potential manipulations of non-resource mechanisms, such as allelopathy, herbivory, disease, or the presence of mycorrhizae, to increase priority eﬀects. This review incorporates recent research on priority eﬀects to draw the outlines of priority eﬀects-based restoration strategies and deﬁne future research questions that need to be addressed to test and improve these strategies.

Microwave soil heating reduces seedling emergence of a wide range of species including invasives

Wed, 31 Jan 2018 00:00:00

de Manon C.M. Hess, Melissa De Wilde, Nicole Yavercovski, Loic Willm, François Mesléard, Elise Buisson
In Restoration Ecology, 10.1111/rec.12668 (2018), 10 pp.
En ligne : onlinelibrary.wiley.com[...]

A microwave-based process to control invasive species (seeds and adult stages) in the field prior to plant community restoration is currently under development. We investigated the effect of four microwave treatment pairings of Power × Duration (2kW4min, 4kW2min, 2kW8min, and 4kW4min) on seedling emergence of (1) an abandoned field seed bank used as a model for various plant species and (2) seeds of three species invasive in Europe: Datura stramonium (Jimson weed), Reynoutria × bohemica (Bohemian knotweed), and Solidago gigantea (Giant goldenrod). In addition, we assessed whether nontreated seeds of these three invasive species could germinate on microwave-treated soils. As microwave soil heating usually leads to nonhomogeneous temperatures within a sample, we also assessed whether the position of seeds in the soil during microwave treatment (center vs. edges) impacted seedling emergence. Results show that the most intensive microwave treatments (2kW8min and 4kW4min), enabling the soil to reach 85°C, are highly effective in inhibiting seedling emergence of invasive species and the seed bank. The 2kW8min treatment, combining lowest power and longest exposure, is the most effective, reducing seed bank seedling emergence by 98% compared to control. The results also reveal a species-specific response to heat, and lower microwave effectiveness on seeds located at the soil surface, which may explain the incomplete effectiveness of intensive treatments. Our results also suggest that prior microwave soil treatment does not prevent a considerable proportion of newly arrived invasive species seeds from germinating, suggesting that this method should be followed by restoration of native plant cover.

Using microwave soil heating to inhibit invasive species seed germination

Fri, 1 Sep 2017 00:00:00

de Melissa De Wilde, Elise Buisson, Nicole Yaverkovski, Loic Willm, Livia Bieder, François Mesléard
In Invasive Plant Science and Management, 10(3) (July-September 2017), 42-51
En ligne : doi.org[...]

Successful invasive plant eradication is rare, because the methods used target the adult stage, not taking into account the development capacity of a large seedbank. Heating by microwave was considered, because it offers a means w quickly reach the temperature required for loss of seed viability and inhibition of germination. Previous results were not encouraging, because homogeneous and deep-wave penetration was not achieved, and the various parameters that can affect treatment effectiveness were incompletely addressed. This study aimed to determine, under experimental conditions, the best microwave treatment to inhibit invasive species seed germination in terms of power (2, 4, 6kW) and duration (2, 4, 8 min) of treatments and depending on soil moisture (10%, 13%, 20%, 30%) and seed burial depth (2, 12cm). Three invasive species were tested: Bohemian knotweed, giant goldenrod, and jimsonweed. The most effective treatments required relatively high power and duration (2kW8min, 4kW4min, 6kW2min, and 6kW4min; 4kW8min and 6kW8min were not tested for technical reasons), and their effectiveness diminished with increasing soil moisture with germination percentage between 0% and 2% for the lowest soil moisture, 0% and 56% for intermediate soit moisture, and 27% and 68% in control treatments. For the highest soil moisture, only 2kW8min and 4kW4min reduced germination percentage between 2% and 19%. Occasiona1ly, germination of seeds located at the 12-cm depth was more strongly affected. Giant goldenrod seeds were the most sensitive, probably due to their small size. Results are promising and justify further experiments before developing a field microwave device to mat large volumes of soil infested by invasive seed efficlently and with reasonable energy requirements. Other types of soil, in terms of texture and argutie matter content, should be tested in future capermonts, because these factors influence soil water content and, consequently, microwave heating.

Photoperiod buffers responses to salt and temperature during germination of two coastal salt marsh colonizers Juncus acutus and Juncus maritimus

Tue, 1 Nov 2016 00:00:00

de François Mesléard, N. Yavercovski, T. Dutoit
In Plant Biosystems, 150(6) (November, 2016), 1156-1164
En ligne : doi.org[...]

Juncus acutus and J. maritimus are two colonizers of coastal marsh rangeland with worldwide distribution. We tested the effect of salt, temperature, and photoperiod on the germination capacity of seeds of the two Juncus from the Rhône delta (south of France). We measured the first day of germination, the mean time, speed, and rate of germination on seeds subjected to five salinity levels, three Dark–Light temperatures and two D-L photoperiods (12–12 and 10–14). The 10–14 D-L photoperiod, although it corresponds to one of the two main germination periods of J. acutus and J. maritimus in the northern Mediterranean, has never been previously used to study their germination capacity. Analyses showed significant effects of salinity and temperature on the germination parameters tested, and for these two factors we found results comparable to those of previous studies. Salinity slowed down and reduced the germination process while spring temperatures had a positive effect. A surprising result was obtained by changing the D-L photoperiod from 12–12 to 10–14 which then largely buffered the negative effect of salt and high temperatures on germination. This capacity of J. acutus and J. maritimus to withstand salty conditions during the germination phase due to the spring photoperiod could be decisive in the ability of both species to colonize saline environments.

Using Different Grazing Practices for Increasing Plant Biodiversity in the Dykes and Embankments Along the Rhône River (Southern France)

Tue, 19 Jul 2016 00:00:00

de Cannelle Moinardeau, François Mesléard, Thierry Dutoit
In Environmental Management, 58(984) (July 2016), 1-14
En ligne : link.springer.com[...]

Extensive grazing by domestic herbivores is a widespread management practice used since the 80s in many European agro-ecosystems such as semi-natural grasslands to maintain open habitats and to enhance biodiversity. Such grazing systems have principally been tested in cultural ecosystems of high nature value threatened by grazing abandonment. However, there have been few case studies of grazing management in very anthropized ecosystems, such as the new ecosystems created by urban or industrial conversions. In Southern France, by the lower part of the Rhône river, since 1999, different low-intensity grazing management systems using rustic breeds of cattle, horses and goats have been tested on a protected reserve of 1454 ha located in the lower part of the Rhône river. Extensive grazing, more than cutting or no management, positively modified vegetation heterogeneity (beta-diversity), the target open grassland species, but not plant species richness (alpha-diversity). However, the current monitoring shows that these benefits of grazing will be confirmed only if low-intensity grazing systems are sustained and if new adaptations can be also made, such as the use of mixed stocking and the establishment of multiyear contracts with breeders./La mise en place d'une gestion par le pâturage de la végétation de la réserve de Donzère Mondragon et la comparaison avec la coupe. Le pâturage se révèle meilleur que la coupe pour augmenter l'hétérogénéité (diversité Beta ) mais, pour l'instant, ne modifie pas significativement la richesse spécifique (diversité alpha). La mise en place d'un pâturage pluri-espèces est suggéré afin d'augmenter l'efficacité du pâturage domestique.

Recasting the dynamic equilibrium model through a functional lens: the interplay of trait-based community assembly and climate

Sun, 1 May 2016 00:00:00

de Jessy Loranger, Cyrille Violle, Bill Shipley, Sandra Lavorel, Anne Bonis, Pablo Cruz, Frédérique Louault, Grégory Loucougaray, François Mesléard, Nicole Yavercovski, et al.
In Journal of Ecology, 104(3) (May 2016), 781-791
En ligne : onlinelibrary.wiley.com[...]

According to the dynamic equilibrium hypothesis (DEH), plant species richness is locally controlled by productivity and disturbance. Given that regional conditions widely affect local environmental variables such as soil nutrient availability, the DEH predictions could be improved by considering how climate influences local controls of species richness. Further, a trait-based approach to community assembly has the potential to reveal a deeper, mechanistic understanding of species richness variation across environments. Here, we bring together DEH and trait-based community assembly expectations to examine whether and how local relationships between diversity, disturbance and productivity are affected by habitat filtering and regional climate.
The authors specifically tested how gradients of local nutrient availability and disturbance intensity interact with climatic conditions to drive the species richness of grassland communities. Further, the authors recast the DEH through a functional lens by exploring how disturbance–diversity and nutrient availability–diversity relationships are shaped by the functional space occupied by species in a community and species packing within this functional space.
The authors’ findings quantitatively highlight the interplay between regional and local environmental gradients in driving community assembly. We demonstrate that, depending on climatic conditions, observed patterns of both taxonomic and functional community composition can be opposite to expected productivity–diversity and disturbance–diversity relationships. This emphasizes the relevance of multifaceted studies of biodiversity and the need for a more systematic quantification of regional controls in community assembly studies.

Impacts of water stress removal and disturbance regimes on Mediterranean dry grasslands diversity and succession

Tue, 1 Sep 2015 00:00:00

de Solène Masson, Gauvain Matthieu, François Mesléard, Dutoit Thierry
In Plant Ecology, 216 (September, 2015)

Our goal was to disentangle the effects of stress removal and disturbance on plant communities of a Mediterranean rangeland, La Crau (southeastern France). We compared undisturbed reference steppe vegetation with vegetation impacted by changes in land use such as earlier phases of cultivation (dating back 20 years) and/or current water infiltrations (revealed by the presence of Brachypodium phoenicoÏdes), since the establishment of adjacent hay meadows. We considered plots with and without brambles (Rubus ulmifolius), an indigenous shrub species that had colonized the area after the land-use changes. We monitored the composition and measured the taxonomic richness and richness of functional groups, evenness and similarities of plant communities. The species richness of the undisturbed community was significantly higher than that of all disturbed plant communities. Although cultivation led to the dominance of ruderal species, the removal of water stress had a stronger negative impact, enabling the establishment of herbaceous competitor species such as B. phoenicoı¨des. The dominance of this species resulted in a significant decline in species richness and evenness after water stress removal. The presence of brambles correlating with former cultivation and/or current water infiltration did not have a significant impact on plant species richness in the vicinity of bramble bushes, although it significantly modified the composition of the adjacent herbaceous vegetation. Our study highlights again the low resilience of Mediterranean dry grasslands after disturbance. While both the disturbance and the water stress removal resulted in changes within the plant community, our findings reveal a stronger impact of the water stress removal. Water infiltration led to decreased plant species richness and evenness because the greater availability of water favored competitor species over the stress-tolerant xeric species. Therefore, for restoring the original steppe species richness, the priority will be to control water infiltrations, even before any scrub-clearing is undertaken to control bramble colonization.

Competition Is a Strong Driving Factor in Wetlands, Peaking during Drying Out Periods

Thu, 1 Jan 2015 00:00:00

de A. Merlin, A. Bonis, C. Damgaard, François Mesléard
In PLOS ONE, 10(6) (June, 2015), e0130152
En ligne : journals.plos.org[...]

The aim of the study is to investigate the relative importance of plant-plant interactions with regard to flooding and drought effect on perennial plant performances in wetlands. Flooding is expected to be the major driver and, accordingly, the importance of drought is hardly if ever taken into account. Focusing on five widespread species, the growth, the survival and the competitive ability of plants were monitored on permanent plots spread along two elevation gradients. Flooding duration and drought intensity were found to vary substantially along the ~ 0.5 meter range elevation gradient. Flooding and drought alternate over the hydrological year and the pin-point surveys were thus conducted over the course of one year. The data were modeled taking into account survival, recruitment and competitive growth throughout flooding and drying out periods. Flooding and drought both directly impacted the plant performances and their competitive effect, with the effect of drought being much more general among species and of higher magnitude than flooding. The importance of competition was found to be high for all species, particularly during the drying out period. It varied more along the flooding gradient than along the drought gradient. The higher flooding tolerance shown by the studied species compared to drought may be related to species specific growth timing together with efficient response traits. These results offer new insights into the filters operating over the species pools. This suggests that the drying out period and drought conditions may be even more important for species’ relative success and the importance of competition than the flooding pattern. The general applicability of this result, obtained in mild Atlantic climate and fertile wetlands, remains to be studied.

Using Shrub Clearing, Draining, and Herbivory to Control Bramble Invasion in Mediterranean Dry Grasslands (2015)

Thu, 1 Jan 2015 00:00:00

de S. Masson, François Mesléard, T. Dutoit
2015, 933–945
En ligne : link.springer.com[...]

For centuries, the dry grassland of the plain of La Crau (south-eastern France) has been subjected to numerous disturbances resulting in the destruction and the fragmentation of this emblematic rangeland ecosystem of the Mediterranean. Today, this ecosystem is facing a new threat from a proliferating native species, the bramble (Rubus ulmifolius Schott), which preferentially colonizes areas that were formerly cultivated and/or exposed to water infiltration. To identify a strategy for effective control of this colonization, in situ experiments testing disturbance regimes (shrub clearing and/or mixed grazing by sheep and goats) combined with the control of access to water resources (with or without drainage trenches) were undertaken between 2010 and 2013. Only clearing and grazing combined over 3 years led to significant changes in vegetation height and bramble cover as well as modifications in the floristic composition, diversity, similarity, and richness of the plant community. Neither a clearing operation carried out in 2010 alone, nor grazing alone, reduced bramble cover, and neither treatment increased the species richness of the plant community. Similarly, digging drainage trenches had no significant impact either on the plant community or on bramble cover. Our study suggests that only annual mechanical clearing coupled with sheep and goats grazing can significantly reduce bramble cover. This combined restoration treatment needs to be applied for at least 3 consecutive years to induce significant changes and enable this ecosystem to return to the dry grassland succession.

Plant trait-digestibility relationships across management and climate gradients in permanent grasslands

Wed, 1 Oct 2014 00:00:00

de Antoine Gardarin, Éric Garnier, Pascal Carrere, Pablo Cruz, Donato Andueza, Anne Bonis, Marie-Pascale Colace, Bertrand Dumont, Michel Duru, Anne Farruggia, et al.
In Journal of Applied Ecology, 51(5) (OCT 2014), 1207-1217

1. Dry matter digestibility is a critical component of herbage nutritive value, a major service delivered by grasslands. The aim of this study was to test whether the dominance hypothesis applies to assess the impacts of environmental gradients and management regimes on this component of herbage nutritive value in permanent grasslands. 2. At the plant level, digestibility has been related to a number of functional traits, but whether this can be scaled up to the community level in species-rich grasslands and how such relationships are modulated by environmental conditions and management regimes remain unknown. Our primary objective was to test whether community-weighted means - species trait values weighted by the species abundance - of morphological, phenological and chemical traits could be used to explain variations in digestibility over a large range of climatic contexts, soil resource levels and management regimes. Our second objective was to explain variations in community digestibility within and among nine contrasting sites along large natural and man-induced environmental gradients. 3. Over the whole data set, digestibility and most community-weighted means of traits responded to climatic factors and management regimes, but relations were not always significant when each site was considered separately. Community digestibility was significantly related to one or more plant traits within each site and to all of the measured traits when considering all the sites. Leaf dry matter content (LDMC) had the most consistent effects on digestibility, with a strikingly similar negative effect within each site. Potential evapotranspiration was negatively related to digestibility and contributed to explain a large part of the among-site variance. In addition, a low return interval of disturbance and a high disturbance intensity (biomass removal) were both associated with a high digestibility. 4. Synthesis and applications. Disturbance regime, plant traits and local climate impacted dry matter digestibility roughly equally in grasslands. The effects of community composition on digestibility and its response to abiotic factors could be successfully captured by community-weighted means of leaf dry matter content. This functional marker can be used to develop indicators and grassland management rules to support farmers in the refinement of their practices towards specific needs, such as target production outputs.

Impacts de différents régimes de perturbations et niveaux de ressource hydrique pour contrôler une espèce proliférante dans un écosystème pseudo-steppique

Tue, 1 Jul 2014 00:00:00

de Solène Masson, François Mesléard, Thierry Dutoit
In Acta Botanica Gallica, 161(3) (July, 2014), 261-275
En ligne : doi.org[...]

Depuis des siècles, la pseudo-steppe de la Crau (sud-est de la France) est soumise à de nombreuses perturbations entrainant destruction et fragmentation de cet écosystème unique au monde. Outre une diminution de la richesse spécifique et une banalisation de la végétation, la communauté végétale est menacée par Rubus ulmifolius Schott qui colonise les milieux anciennement cultivés et/ou soumis à des infiltrations hydriques venant de l’irrigation des prairies de foin voisines. L’augmentation de son recouvrement entraine une diminution des surfaces herbacées disponibles pour le pâturage ovin, responsable de l’organisation et de la structure de la formation végétale.

Afin de comprendre cette colonisation, des expérimentations in situ testant différents régimes de perturbation (débroussaillage et/ou pâturage) croisés à différents niveaux d’humidité du sol ont été menées de novembre 2010 à septembre 2013. Nos résultats mettent en évidence des changements significatifs de composition et une augmentation de la richesse spécifique entre les placettes débroussaillées et pâturées annuellement et celles qui ne l’étaient pas. Néanmoins l’action unique d’un débroussaillage ou du pâturage n’a pas permis de maintenir le milieu ouvert. Pour contrôler cette dynamique, un débroussaillage annuel couplé à un retour du pâturage ovin est donc recommandé. De plus; la restauration du réseau d’irrigation est à envisager afin de limiter la présence de Brachypodium phoenicoides (L.) Roem. & Schult. qui se développe au dépend des espèces de la steppe. / The plain of la Crau, located in South Eastern France, is a unique pseudo-steppe ecosystem, characterized by the presence of a Mediterranean climate, stony soil and limestone conglomerate at 40cm depth, and a traditional sheep grazing dating back to 6,000 years. Nevertheless, for many decades, this ecosystem has been subjected to numerous exogenous disturbance regimes. Indeed, during the 16th century, the construction of channels led to the transformation of the dry grasslands into hay meadows. Moreover, during the last century, agriculture intensification and the industrial development of military activities have significantly altered the steppe. Now, the plain of la Crau is a fragmented landscape where steppe habitats are connected directly with irrigated orchards or hay meadows. The effects on plant communities have been a decrease of species richness, a trivialization of plant composition and also the colonization of disturbed areas by pioneer invasive species such as Rubus ulmifolius Schoot, the elm leaf bramble. Absent from the original plant composition, this species can colonize areas formerly cultivated and/or subjected to water infiltrations coming from the mismanagement of the irrigation of hay meadows nearby. The increase of bramble cover is a threat to the Crau, because it causes the reduction of herbaceous community available for traditional sheep grazing, which is responsible for the organization and the structure of the steppe plant communities. To better understand this phenomenon and to discriminate the factors responsible for this colonization, an experimentation in situ based on the implementation of different disturbance regimes (shrub clearing and/or grazing) crossed with two levels of water resources has been carried out during three years (between November 2010 to September 2013). During this period, we have performed a monitoring of the vegetation each spring and measured the photosynthetically active radiation at different times to a year (at the moment of clearing, before and after grazing, and after the summer drought).Our results evidence significant changes in the composition and a drastic increase of species richness between plots that were cleared and grazed each year and those that were not. These differences can be explained by a significant reduction in the area occupied by the bramble (increase of photosynthetically active radiation). However, the action of a single clearing or grazing alone did not succeed in maintaining an open environment. No significant action of the drying plots could be detected on the plant community and on the dynamics of brambles. In order to perform a potential ecological restoration, an annual clearing coupled with a return of sheep grazing is recommended. In addition, the restoration of the irrigation system is considered in the discussion to limit the presence of Brachypodium phoenicoides (L.) Roem. & Schult that develops probably at the expense of typical steppe species.

Effect of topsoil removal and plant material transfer on vegetation development in created Mediterranean meso-xeric grasslands

Tue, 1 Apr 2014 00:00:00

de Isabelle Muller, François Mesléard, Elise Buisson
In Applied Vegetation Science, 17(2) (2014), 246-261
En ligne : onlinelibrary.wiley.com[...]

Question Can plant material transfer combined with topsoil removal be an efficient method of restoring Mediterranean meso-xeric grassland plant communities? Does increasing topsoil removal depth increase the success of plant material transfer establishment? Location The Camargue, Rhône delta, France. Methods A small-scale restoration experiment involving Mediterranean meso-xeric grasslands was conducted in a former rice field area. During 3 yr, plant species richness and composition were compared on permanent plots subject to the following four treatments: 5 cm topsoil removal, 20 cm topsoil removal, 5 cm topsoil removal with plant material transfer, and 20 cm topsoil removal with plant material transfer. Additionally, the seed bank at 0- to 5-cm deep, at 5- to 20-cm deep and at 20- to 40-cm deep were studied in order to evaluate the effect of topsoil removal. Results After 4 mo, species richness, number of target species and similarity to the reference Mediterranean meso-xeric grassland significantly increased with plant material transfer relative to the no transfer treatment (topsoil removal without transfer). However, we found no significant difference in plant species number between the two depths of topsoil removal. This can be explained by the absence of any variation in soil seed bank between 5 cm and 20 cm. The species richness and number of target species decreased significantly in transfer treatment between the first and the second monitoring. Despite this general decrease in the first year, the plant material transfer treatment showed significantly more target species than the no transfer treatment and a higher similarity to the Mediterranean meso-xeric grassland. Conclusion In order to restore a Mediterranean meso-xeric grassland plant community, plant material transfer combined with topsoil removal appears to be a relevant method. Removing 5 cm of topsoil eliminates half of the density of the undesired seed bank in a former rice field. However, the ability of target species to establish and persist in restored vegetation communities will require good management. Conditions with low competition in early stages of succession seem to be essential for transferred species to persist, and appropriately timed grazing and adequate stocking rates will be needed to limit the negative effects of competition.

Impacts of disturbance regimes and rates of water resource levels in the control of bramble colonization in a pseudo-steppe ecosystem: the case of the plain of la Crau (2014)

Wed, 1 Jan 2014 00:00:00

de S. Masson, François Mesléard, T. Dutoit
2014, 261-275
En ligne : www.cabdirect.org[...]

The plain of la Crau, located in South Eastern France, is a unique pseudo-steppe ecosystem, characterized by the presence of a Mediterranean climate, stony soil and limestone conglomerate at 40 cm depth, and a traditional sheep grazing dating back to 6,000 years. Nevertheless, for many decades, this ecosystem has been subjected to numerous exogenous disturbance regimes. Indeed, during the 16th century, the construction of channels led to the transformation of the dry grasslands into hay meadows. Moreover, during the last century, agriculture intensification and the industrial development of military activities have significantly altered the steppe. Now, the plain of la Crau is a fragmented landscape where steppe habitats are connected directly with irrigated orchards or hay meadows. The effects on plant communities have been a decrease of species richness, a trivialization of plant composition and also the colonization of disturbed areas by pioneer invasive species such as Rubus ulmifolius Schoot, the elm leaf bramble. Absent from the original plant composition, this species can colonize areas formerly cultivated and/or subjected to water infiltrations coming from the mismanagement of the irrigation of hay meadows nearby. The increase of bramble cover is a threat to the Crau, because it causes the reduction of herbaceous community available for traditional sheep grazing, which is responsible for the organization and the structure of the steppe plant communities. To better understand this phenomenon and to discriminate the factors responsible for this colonization, an experimentation in situ based on the implementation of different disturbance regimes (shrub clearing and/or grazing) crossed with two levels of water resources has been carried out during three years (between November 2010 to September 2013). During this period, we have performed a monitoring of the vegetation each spring and measured the photosynthetically active radiation at different times to a year (at the moment of clearing, before and after grazing, and after the summer drought). Our results evidence significant changes in the composition and a drastic increase of species richness between plots that were cleared and grazed each year and those that were not. These differences can be explained by a significant reduction in the area occupied by the bramble (increase of photosynthetically active radiation). However, the action of a single clearing or grazing alone did not succeed in maintaining an open environment. No significant action of the drying plots could be detected on the plant community and on the dynamics of brambles. In order to perform a potential ecological restoration, an annual clearing coupled with a return of sheep grazing is recommended. In addition, the restoration of the irrigation system is considered in the discussion to limit the presence of Brachypodium phoenicoides (L.) Roem. & Schult that develops probably at the expense of typical steppe species.

Temporary wetland restoration after rice cultivation: is soil transfer required for aquatic plant colonization?

Sun, 1 Sep 2013 00:00:00

de I. Muller, E. Buisson, Jean-Baptiste Mouronval, François Mesléard
In Knowledge and Management of Aquatic Ecosystems, 411 (September, 2013), 03
En ligne : www.kmae-journal.org[...]

Mediterranean temporary wetlands have considerably declined in recent decades. Today, opportunities arise for the restoration of these wetlands due to land-use changes, such as the abandonment of cultivation. One critical question is whether communities, such as those observed in natural temporary wetlands, can develop alone or if active restoration should be implemented. In a series of experimental mesocosms, we transferred soil from several temporary wetlands chosen as a set of reference ecosystems. Four months after soil transfer, vegetation in transfer mesocosms was compared to that derived from spontaneous colonization (control mesocoms). Transfer mesocosms are colonized by all target hydrophyte species transferred with the soil and the resulting communities are similar to those of reference ecosystems. They also have fewer non-target species than the control mesocosms. Even though the study period was not sufficient to draw any definitive conclusion regarding the utility of forced dispersion by soil transfer, the preliminary results are promising for an application on a larger scale.

New synthetic indicators to assess community resilience and restoration success (2013)

Tue, 1 Jan 2013 00:00:00

de R. Jaunatre, E. Buisson, I. Muller, H. Morlon, François Mesléard, T. Dutoit
2013, 468-477
En ligne : www.sciencedirect.com[...]

The Strategic Plan for Biodiversity 2011–2020 sets as an objective the restoration of 15% of degraded ecosystems by 2020. This challenge raises at least two major questions: (i) How to restore and (ii) how to measure restoration success of said ecosystems? Measurement of restoration success is necessary to assess objective achievement and to adjust management with regard to objectives. Numerous studies are being conducted to try to work out synthetic indices to assess ecosystem diversity or integrity in the context of global change. Nevertheless, at the community level, there is no index that allows the assessment of community integrity regarding its restoration or resilience, despite the fact that a lot of indicators are used such as species richness, Shannon diversity, multivariate analyses or similarity indices. We have therefore developed two new indices giving new insights on community states: the first index, coined as the Community Structure Integrity Index, measures the proportion of the species abundance in the reference community represented in the restored or degraded community, and the second index, coined as the Higher Abundance Index, measures the proportion of the species abundance in the restored or degraded community which is higher than in the reference community. We illustrate and discuss the use of these new indices with three examples: (i) fictitious communities, (ii) a recent restoration (2 years) of a Mediterranean temporary wetland (Camargue in France) in order to assess restoration efficiency, and (iii) a recently disturbed pseudo-steppe plant community (La Crau area in France) in order to assess natural resilience of the plant community. The indices provide summarized information on the success of restoration or on the resilience of the plant community, which both appear less positive than with standard indicators already used. The indices also provide additional insights useful for management purposes: the Community Structure Integrity Index can indicate whether the improving target species abundance is needed or not while the Higher Abundance Index can indicate whether controlling the high abundance of some species is needed in order to approach a reference ecosystem. These relatively simple indices developed on community composition and structure state can provide a base to further indices focusing on ecosystem functioning or services not only calculating values as a static point but also its temporal or spatial dynamic.

Habitat requirements and population structure of the rare endangered Limonium girardianum in Mediterranean salt marshes

Sun, 1 Apr 2012 00:00:00

de Teddy Baumberger, Laurence Affre, Thomas Croze, François Mesléard
In Flora, 207(4) (April, 2012), 283-293
En ligne : www.sciencedirect.com[...]

The sea lavender Limonium girardianum (Guss.) Fourr. is endemic to the Mediterranean salt marshes of the French and Spanish coasts. Most of the salt marshes where L. girardianum occurs are exposed to human disturbance, in particular due to industrial expansion. To determine the ecological conditions favorable to the development of L. girardianum, we used a set of permanent plots distributed along a topographical gradient in eleven French salt marshes. We monitored intensity of flooding, water table depth, soil moisture, soil salinity and granulometry. We investigated (i) the abiotic and biotic requirements for L. girardianum and (ii) the effects of environmental conditions on the population structure of L. girardianum. We found a unimodal response of L. girardianum species to flooding, salt and soil moisture gradients. Soil texture modulated the effects of flooding and drought on the presence of the species. Furthermore, flooding induced population renewal, i.e. the highest seedling emergence and adult mortality. We recorded low seedling emergence in higher topographical positions. Proportions of seedlings were lowest on saltier soils and highest in flooded areas and on coarse sand. Prolonged flooding is likely to induce population renewal as long as remaining individuals are capable of reconstituting viable populations. To suggest efficient intermediate and long-term conservation strategies for L. girardianum, it will be necessary to consider the role of human-driven changes in salt marshes with regard to hydrology and control of the vegetation.

Co-occuring species indicate habitats of the rare Limonium girardianum (2012)

Sun, 1 Jan 2012 00:00:00

de T. Baumberger, T. Croze, L. Affre, François Mesléard
2012, 31-37(7)
En ligne : www.ingentaconnect.com[...]

Background and aims – The conservation of a rare and endangered plant species requires a clear knowledge of its habitat distribution. Species Distribution Models (SDM) are generally applied to characterize species' suitable habitats and to predict their potential distribution. However, this method is not well suited to rare species that require a fine spatial scale approach. Co-occurring plant species of a targeted species can be used to define suitable habitats taking into account biotic interactions. Our aim was to construct a predictive model of the presence of the rare Limonium girardianum, using the species that are the best indicators of its presence.
Methods – In the main sites in the French coastal salt marshes where L. girardianum occurs, we investigated 198 quadrats (1 × 1 m) with and without L. girardianum in three strata along a topographical gradient. In these quadrats, we recorded plant species and measured the maximum water level during flooding, the soil moisture, salinity and texture. We calculated the species indicator value of the presence of L. girardianum . For each quadrat, we added the species indicator values to obtain a score used to model the presence of L. girardianum. We compared the predictive power of the model based on co-occurring plant species with a model based on environmental variables.
Key results – The best indicator species of the presence of L. girardianum are Limonium virgatum , Hymenolobus procumbens and Frankenia pulverulenta. The predictive power of the model based on the co-occurring plant species appears to be similar to that of the model based on environmental variables, with about 72% of correct predictions. However, the environmental model shows higher False Positive predictions than the plant species model.
Conclusions – The co-occurring plant species can be used to define suitable habitats for L. girardianum. The model based on the co-occurring plant species, that integrates the biotic interactions, would appear to be more efficient to define the habitat where L. girardianum is most likely to be found. Furthermore, as extensive and numerous vegetation databases are available, this simple method could be used to predict the presence of several species with low abundance.

Effects of experimental submersion on survival, growth, and dry biomass allocation of the rare salt marsh plant Limonium girardianum (2012)

Sun, 1 Jan 2012 00:00:00

de T. Baumberger, François Mesléard, T. Croze, L. Affre
2012, 65-70
En ligne : www.sciencedirect.com[...]

In order to define the flooding tolerance capacity of Limonium girardianum according to growth development stage, we submerged 200 seedlings and 200 four-month-old juveniles in fresh water. During the eleven weeks of the experiment, we recorded the survival, growth and dry biomass of both seedlings and juveniles. Every week, we removed a group of ten seedlings and ten juveniles from submerged conditions and put them in drained conditions. We measured the leaf production rate and variation in total leaf area of both seedlings and juveniles. We measured the final above and below-ground dry biomass for both seedlings and juveniles. The seedlings started to die from week-2, while juveniles started to die from week-7. Fifty percent of seedlings died over a six weeks period, while fifty percent of juveniles died over a ten-week period. Beyond seven weeks and nine weeks for seedlings and juveniles respectively, total submersion stopped growth, and delayed leaf production and the increase of the total leaf area. Above-ground dry biomass significantly decreased from 30 g to 10 g for seedlings and from 30 g to 25 g for juveniles, according to flood duration. Below-ground dry biomass percentage increased from 60% to 80% between week-4 and week-7 for seedlings. Below-ground dry biomass of juveniles decreased from 80% to 50% between week-4 and week-9. Our study showed that flood-prone plant species have a different response to flood conditions according to the developmental stage. The higher sensitivity to submersion of seedlings is due to its lower survivorship, lower leaf production, lower growth and more important dry biomass decrease than juveniles. This statement can be seen as a threat for population viability in the long term since human activities, such as construction of heavy industrial infrastructures and roads, induces too long flood duration that would compromise the persistence of L. girardianum populations.

When does grazing generate stable vegetation patterns in temperate pastures? (2012)

Sun, 1 Jan 2012 00:00:00

de B. Dumont, N. Rossignol, G. Loucougaray, P. Carrere, J. Chadoeuf, G. Fleurance, A. Bonis, A. Farrugia, S. Gaucherand, C. Ginane, et al.
2012, 50-56
En ligne : www.sciencedirect.com[...]

The stability of grazing-induced spatial patterns of vegetation was analyzed at two spatial scales (25 m × 20 m areas and 1.6 m × 0.8 m grids) in pastures of contrasting productivity (maximum standing biomass: 130–800 gDM/m2). At both scales, the mosaic of grazed and ungrazed patches was modeled as a Boolean process, calculating cross-variograms to quantify the temporal stability of grazing patterns and its links with local floristic composition were tested. The scale at which stability of vegetation patterns took place in two successive years depended on pasture productivity. Inter-annual stability of large-scale patterns mainly occurred in extensively used fertile pastures grazed by cattle, and in pastures grazed by horses. Less-fertile grasslands were mainly characterized by a fine-scale stability of grazing patterns. Stable fine-scale patterns were often related to the local abundance of legumes and forbs. Stable large-scale patterns of grazing within lightly grazed productive grasslands could result in divergent local vegetation dynamics, which can be seen as an opportunity for restoring biodiversity in fertile grasslands.

The demography of space occupancy: measuring plant colonization and survival probabilities using repeated pin-point measurements

Tue, 1 Feb 2011 00:00:00

de Christian Damgaard, Amandine Merlin, François Mesléard, Anne Bonis
In Methods in Ecology and Evolution, 2(1) (February, 2011), 110–115
En ligne : besjournals.onlinelibrary.wiley.com[...]

The study of plant demography has long been an important component of plant ecological studies. However, in plant communities, e.g. grasslands, where individual plants are not easily distinguished and often vary in size, a convenient method of describing the demography and its ecological consequences has been lacking.
The aim of this study was to discuss the potential for using the change in the probability of space occupancy as a measure of ecological success in plant population biology. This will be done by demonstrating how the change in the probability of space occupancy depends on the processes of colonization and survival, and demonstrating how colonization and survival probabilities may be estimated from repeated pin‐point recordings at the same pin‐position. Furthermore, it will be demonstrated how to calculate the sensitivity and elasticity of the change in the probability of space occupancy to colonization and survival probabilities.
The method is applied to a case of repeated pin‐point data of the perennial grass Brachypodium phoenicoïdes that underwent different grazing regimes from 2001 to 2008 on xero‐halophytic grasslands.
It was demonstrated that grazing affected both plant survival and colonization probabilities so that the estimated colonization and survival probabilities of B. phoenicoïdes were highest in the non‐grazed regime. Furthermore, using the calculated elasticity of the change in space occupancy, we found that survival was more important than colonization events in determining the ecological success of B. phoenicoïdes in the non‐grazed regime, whereas colonization events were more important than survival in the grazed regime.
Synthesis and applications. We expect that the relatively simple method may be widely used on existing and future repeated pin‐point recordings from the same pin‐position and, consequently, that plant demographic questions may be addressed with larger precision in plant communities where individual plants are not easily distinguished.

Rabbits are more effective than cattle for limiting shrub colonization in Mediterranean xero-halophytic meadows (2011)

Sat, 1 Jan 2011 00:00:00

de François Mesléard, André Mauchamp, Olivier Pineau
2011, 37-41
En ligne : www.tandfonline.com[...]

Mediterranean xero-halophytic meadows are a priority habitat for conservation in the European Union. In the Camargue (Rhône delta, south of France), these meadows are heavily colonized by Phillyrea angustifolia shrub. In order to evaluate the respective roles of livestock and rabbits in Phillyrea control, we recorded and aged Phillyrea individuals in meadows subjected to 3 different treatments: grazing by rabbit plus traditional extensive grazing by cattle and horses from the beginning of the 1970s, grazing by rabbit only, and grazing by rabbit only with their temporary elimination in 1987. We found little difference in either the age distribution or the density of Phillyrea individuals between meadows grazed and ungrazed by domestic herbivores. In meadows where rabbits were temporarily eliminated we recorded a strong increase in the number of Phillyrea individuals from the time of this exclusion onwards. In addition, we aged Phillyrea shrubs in 35-y-old experimental plots grazed by cattle, horses, and rabbits, grazed by rabbits only, or ungrazed by livestock or rabbits. We found 90% of Phillyrea individuals in the plots ungrazed by rabbits. Thus, the current decline of rabbit populations appears to be a new threat for Mediterranean xero-halophytic meadows / Les prairies xéro-halophyles méditerranéennes sont un habitat prioritaire pour l'Union européenne. En Camargue (delta du Rhône, sud de la France), elles sont fortement colonisées par l'arbuste Phillyrea angustifolia. Afin d'évaluer le rôle respectif des herbivores domestiques et du lapin dans le contrôle du Phillyrea, nous avons recensé et daté les individus de Phillyrea dans des prairies soumises à 3 traitements différents: un pâturage par les lapins plus un pâturage extensif par des taureaux et des chevaux depuis le début des années 1970, un pâturage par des lapins exclusivement, ainsi qu'un pâturage par les lapins, mais incluant une élimination temporaire de ceux-ci en 1987. Nous avons trouvé peu de différences dans la distribution d'âges et la densité des individus de Phillyrea entre les prairies pâturées et non pâturées par des herbivores domestiques. Dans les praires où les lapins ont été temporairement éliminés, nous avons mis en évidence une forte augmentation du nombre d'individus de Phillyrea à la suite de cette élimination. Nous avons également recensé les individus de Phillyrea dans d'anciens exclos expérimentaux de 35 ans, pâturés par des lapins, des taureaux et des chevaux, pâturés exclusivement par les lapins ou non pâturés. Nous avons recensé 90 % des individus de Phillyrea dans les exclos non pâturés par les lapins. Dans ce contexte, le déclin actuel des populations de lapin apparaît comme une nouvelle menace pour ces prairie